1. Field of the Invention
The invention relates to a method for fabricating a light-emitting device. More particularly, the method provides a wafer with light-emitting devices, and obtains the wavelengths of every light-emitting device. It then forms different doses of phosphor on the light-emitting devices according to their wavelengths, and obtains the light-emitting devices with uniform color temperature.
2. Description of the Related Art
FIGS. 1A to FIG. 1G illustrate a conventional method of fabricating a light-emitting device. As shown in FIG. 1A, an n-type cladding layer 19 is formed on an insulating substrate 18 in the semiconductor process. Next, as shown in FIG. 1B, a p-type cladding layer 22 is formed on the n-type cladding layer 19. Next, as shown in FIG. 1C, a p-type electrode 17 is formed on the p-cladding layer 22 and a n-type electrode 14 is formed on the n-type cladding layer 19. Next, as shown in FIG. 1D, a plurality of segment lines L for obtaining a plurality of light-emitting die by cutting thereon is formed on the wafer. Next, as shown in FIG. 1E, the light-emitting die is positioned on a first lead frame 12. A first wire 21 connects the p-type electrode 17 and a second lead frame 13, and a second wire 23 connects the n-type electrode 14 and the first lead frame 12. Next, as shown in FIG. 1F, a phosphor layer is formed on the light-emitting device 32. Finally, as shown in FIG. 1G, the light-emitting device 32 is molded in resin 34.
In the conventional method, the dose and composition of the phosphor layer that is formed on each die is substantially the same. However, each light-emitting die can not emit the same wavelength even though the dies were formed on the same wafer by the same semiconductor process. A part of the first wavelength emitted from the light-emitting die is transformed into a second wavelength, which is longer than the first wavelength, by the phosphor. Because of the same dose and composition of the phosphor layer and the different first wavelengths, the second wavelengths emitted from each die aren not the same. Furthermore, the superposed wavelength of the first and second wavelengths from each light-emitting device would not be the same. In other words, each light-emitting device can not have uniform color temperature. Therefore, the yield of the light-emitting devices on a wafer is only 10%.
To solve the above problems, it is an object of the present invention to provide a method for fabricating a light-emitting diode with uniform color temperature, comprising the steps of: forming a plurality of light-emitting diodes on a wafer; obtaining the light emission wavelengths of the light-emitting diodes on the wafer; and forming different doses of phosphor on the corresponding light-emitting diode on the wafer according to the light emission wavelengths of respective light-emitting diodes. Finally, the light-emitting diodes on the wafer emit light with uniform color temperature.
It is another object of the invention to provide a method for fabricating a light-emitting device with uniform color temperature, comprising the steps of: forming a plurality of light-emitting diodes on a wafer; obtaining the light emission wavelengths of the light-emitting diodes on the wafer; forming different doses of phosphor on the corresponding light-emitting diode on the wafer according to the light emission wavelengths of respective light-emitting diodes, so as to provide the light-emitting diodes on the wafer with uniform color temperature; dividing the light-emitting diodes on the wafer into a plurality of light-emitting dies with uniform color temperature; and obtaining the light-emitting device with uniform color temperature by packaging the respective light-emitting die.
It is another object of the invention to provide a method for fabricating a white LED with uniform color temperature, comprising the steps of: forming a plurality of UV/blue LEDs on a wafer; obtaining the light emission wavelengths of the UV/blue LEDs on the wafer; and forming different doses of phosphor on the corresponding UV/blue LED on the wafer according to the light emission wavelengths of respective UV/blue LEDs, so as to provide the white LEDs with uniform color temperature on the wafer.
It is another object of the invention to provide a method for fabricating a white light-emitting device with uniform color temperature, comprising the steps of: forming a plurality of UV/blue LEDs on a wafer; obtaining the light emission wavelengths of the UV/blue LEDs on the wafer; forming different doses of phosphor on the corresponding UV/blue LED on the wafer according to the light emission wavelengths of respective UV/blue LEDs, so as to provide the white LEDs with uniform color temperature on the wafer; dividing the white LEDs on the wafer into a plurality of white light-emitting dies with uniform color temperature; and obtaining the white light-emitting device with uniform color temperature by packaging the respective white light-emitting die.
The invention has a feature of forming different doses of phosphor on the corresponding light-emitting diode. The superposed wavelengths of each light-emitting diode, which are modulated by the first wavelength from the diode and the second wavelength from the phosphor, have almost the same color temperature. The invention can thus increase yield.
The invention has another feature of forming different doses of phosphor on the corresponding light-emitting diode in the wafer form. The invention is different from the conventional method, wherein the phosphor is formed on the light-emitting die after dividing each diode of the wafer in the prior art. Therefore, each wafer can produce a greater quantity of light-emitting devices with uniform color temperature.